The invention relates to a power supply component for a wire electrode of an electroerosion machine.
Such fixed power components along which a wire electrode moves are generally known and are e.g. described in EP-A1-No. 0 128 958 or JP-OS No. 56-76 334.
In the case of known power supply components of this type, the wire cuts into the component, so that the latter component has a relatively short service life. These components have to be realigned after a relatively short time to ensure that the wire does not run into a cut notch, or alternatively these components must be replaced relatively frequently.
JP-OS No. 60-167 720 proposes the solution of this problem by forming the power supply component from superhard, electrically conductive material and to provide therein a guide groove for the wire.
Instead of this, DE-OS No. 31 22 205 proposes a rotary power supply component, in which the rotation axis is at right angles to the wire and consequently a tangentially sliding electric contact is formed.
A power supply component for a wire cutting machine must satisfy the four following requirements:
1. It must ensure a good electric contact. PA0 2. It must be almost non-wearing and therefore have a long service life. PA0 3. To a certain extent it must guide the wire. PA0 4. It must damp vibrations of the wire. PA0 1. Good electric contact PA0 2. Almost no wear. PA0 3. Good wire guidance. PA0 4. Wire vibration damping.
In the power supply components referred to hereinbefore the necessary limited wearing does not occur. There is also the additional disadvantage that in the case of deeper notches cut by the wire, automatic wire threading is made difficult after a wire breaks.
In the case of rotary power supply components of DE-OS No. 31 22 205 the above requirements 3 and 4 are not satisfied, because the tangential sliding contact on the end face of the rotating cylindrical power supply means cannot bring about any guidance and damping and in fact undesired wire vibrations are caused.
The power supply component of JP-OS No. 60-167 720 with the superhard material and the guide groove admittedly fulfills requirements 2 and 3, but the electrical conductivity of hard metals is relatively poor as compared with good conducting metals, such as copper and the like. In addition, with super hard metal, the contact surface between wire and power supply means is very small and there is only a line contact. The guide groove provided there also leads to no significant improvement. If the guide groove is in the form of a V-shaped groove, the wire, which has a circular cross-section, is in contact with said groove along two lines. If the guide is made U-shaped, a larger contact surface is only obtained if the arc of the guide groove precisely coincides with the wire diameter. Thus, a separate guide groove must be provided for each wire diameter. Moreover said wire guide does not satisfy requirement 4 regarding good vibration damping. Finally the prefabricated wire guide must be precisely aligned with respect to the wire.
The problem of the present invention is therefore to improve the power supply means of the aforementioned type in that it simultaneously fulfills the following four requirements: